alter pluggable database pdb prepare mirror copy pdbcopy, ORA-15385: file group ... does not exist

1. I have created pluggable database

2. Converted normal diskgroup into flex

3. Trying to create ASM Clone of a PDB, getting error:

SQL>  alter pluggable database pdb prepare mirror copy pdbcopy;

alter pluggable database pdb prepare mirror copy pdbcopy

*

ERROR at line 1:

ORA-15385: file group 'ORCLPDB_PDB' does not exist

4. Tried to create file group manually using the following command:

SQL> alter diskgroup DATA02 add filegroup ORCLPDB_PDB  DATABASE PDB;

5. Still getting ORA-15385: file group 'ORCLPDB_PDB' does not exist

The problem here is that PDB was created before diskgroup became flex and file groups were not automatically created.